Changing the folder/file permissions to 777 did not work, but the solution provided here did, please read through to that article to understand the issue, its a server-side thing, not theme issue. You might encounter other permission issues in the future because of this.
I did go ahead and install a couple of plugins and import the renew 2 demo to test and it did work.
And please update your Wordpress to the latest version (5.0.3) to avoid incompatibility issues. right now your Wordpress version is outdated (4.7)
And another thing, few things on your server does not meet the Wordpress requires (see here), notably the PHP Version and Database server version, please contact your hosting support to resolve this.
Hope it helps,